在pyqt中缩放和平移小部件

Question

我制作了一个自定义滚动小部件，并实现了缩放和平移。现在的问题是，它不会放大子窗口小部件，平移也不会从当前位置平移，而是滚动回初始位置。(注意：使用鼠标中键平移，使用ctrl+滚轮放大和缩小(

import sys
from PyQt5 import QtWidgets, QtCore
from PyQt5.QtCore import Qt, QSize, QPoint
from PyQt5 import QtWidgets
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *

class ScrollArea(QWidget):
_style = '''
QScrollArea{
background: white;
}

QScrollBar:handle{
background: gray;
max-width: 20px;
color:green;

}
'''
factor = 1.5
def __init__(self, parent=None):
super(ScrollArea, self).__init__()
self.v_layout = QVBoxLayout(self)
self.v_layout.setContentsMargins(0, 0, 0, 0)
self.v_layout.setSpacing(0)
self.container_widget = QWidget()
# Scroll Area Properties
self.scroll = QScrollArea()
self.scroll.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
self.scroll.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
self.scroll.setWidgetResizable(False)
self.scroll.setWidget(self.container_widget)
self.scroll.setStyleSheet(ScrollArea._style)
l = QLabel('Hello world', self.container_widget)
l.setStyleSheet('color: red; font-size: 30px')

self.container_widget.setGeometry(0, 0, self.width(), self.height())

self.v_layout.addWidget(self.scroll)
self.setLayout(self.v_layout)
self._zoom = 0
self.mousepos = QPoint(0, 0)
self.setMouseTracking(True)
self.showMaximized()
def fitInView(self, scale=True):
rect = QtCore.QRectF(self._photo.pixmap().rect())
if not rect.isNull():
self.setSceneRect(rect)
if self.hasPhoto():
unity = self.transform().mapRect(QtCore.QRectF(0, 0, 1, 1))
self.scale(1 / unity.width(), 1 / unity.height())
viewrect = self.viewport().rect()
scenerect = self.transform().mapRect(rect)
factor = min(viewrect.width() / scenerect.width(),
viewrect.height() / scenerect.height())
self.scale(factor, factor)
self._zoom = 0
def wheelEvent(self, wheel_event):
if wheel_event.modifiers() == Qt.ControlModifier:
delta = wheel_event.angleDelta().y()
if delta > 0:
self.zoom_in()
elif delta < 0:
self.zoom_out()
else:
return super().wheelEvent(wheel_event)
def mousePressEvent(self, event):
cursor = self.container_widget.cursor().pos()
print(cursor)
if event.button() == Qt.MidButton:
self.setCursor(Qt.OpenHandCursor)
super(ScrollArea, self).mousePressEvent(event)
def mouseMoveEvent(self, event):
delta = event.localPos() - self.mousepos
# panning area
if event.buttons() == Qt.MidButton:
h = self.scroll.horizontalScrollBar().value()
v = self.scroll.verticalScrollBar().value()
self.scroll.horizontalScrollBar().setValue(int(h - delta.x()))
self.scroll.verticalScrollBar().setValue(int(v - delta.y()))
self.mousepos = event.localPos()
super(ScrollArea, self).mouseMoveEvent(event)
def mouseReleaseEvent(self, event):
self.unsetCursor()
self.mousepos = event.localPos()
super(ScrollArea, self).mouseReleaseEvent(event)
def resizeEvent(self, event):
self.container_widget.resize(self.width(), self.height())
super(ScrollArea, self).resizeEvent(event)
def resize_container(self, option):
option = int(option)
if option == 0:
self.container_widget.resize(self.width()+50, self.height())
elif option == 1:
self.container_widget.resize(self.width()+50, self.height())
elif option == 2:
self.container_widget.resize(self.width()+50, self.height()+50)
@QtCore.pyqtSlot()
def zoom_in(self):
self.container_widget.setGeometry(200, 200, self.container_widget.width() + 4,
self.container_widget.height() + 4)
@QtCore.pyqtSlot()
def zoom_out(self):

self.container_widget.setGeometry(0, 0, self.container_widget.width() - 4,
self.container_widget.height() - 4)

if __name__ == '__main__':
a = QtWidgets.QApplication(sys.argv)
q = ScrollArea()
q.show()
sys.exit(a.exec_())

一旦执行，你会发现标签不会改变大小，一次又一次的平移会导致奇怪的行为。

注意：我发现缩放只是调整容器的大小，有没有一种方法可以正确地放大和缩小

Answer 1

修复平移功能的一种方法是为初始鼠标中键单击添加mousepos的更新：

def mousePressEvent(self, event):
cursor = self.container_widget.cursor().pos()
print(cursor)
if event.button() == Qt.MidButton:
self.setCursor(Qt.OpenHandCursor)
self.mousepos = event.localPos() # <== add this

否则，mouseMoveEvent中的delta是根据旧数据计算的，从而产生"；怪异的"；行为

对于缩放部分；变通办法"；通过增加标签的字体大小：

在init部分创建一个标签和一个字体大小属性：

self.label = QLabel('Hello world', self.container_widget)
self.font_size = 30
self.label.setStyleSheet(f'color: red; font-size: {self.font_size}px')

用下面的"；字体大小修饰符"：

@QtCore.pyqtSlot()
def zoom_in(self):
self.font_size = min(1000, self.font_size + 1)
self.label.setStyleSheet(f'color: red; font-size: {self.font_size}px')
self.label.adjustSize()
@QtCore.pyqtSlot()
def zoom_out(self):
self.font_size = max(2, self.font_size - 1)
self.label.setStyleSheet(f'color: red; font-size: {self.font_size}px')
self.label.adjustSize()

这至少造成了放大的错觉